Intracisternal A particles in preimplantation embryos of feral mice (Mus musculus).

In embryos of feral mice, intracisternal A particles (IAP) are not observed in zygotes, but large numbers are seen budding into the endoplasmic reticulum at the 2-cell stage. In subsequent cleavage stages very few IAP are present. Organelles and developmental changes in organelles during the preimplantation period are characteristic of those described previously in embryos of laboratory mice.